Air conditioning



Ma 12, 1942. A. B. NEWTON AIR CONDITIONING Filed April 17, 1939 perature in Patented May 12, 1942 AIR CONDITIONING Alwin B. Newton, Minneapolis, Minn., assignor to- Minneapolis-Honeywell Regulator Company, Minneapolis, Minn, a corporation of Delaware Application April 17, 1939, Serial No. 268,234 9 Claims. (01. 62-6) This invention relates to air conditioning sys tems. and more particularly to systems for cooling and "dehumidifying the air in a space.

One of the'objects of my invention is to operate a cooling coil over which ai to be conditioned is circulated. in such a manner that substantially complete drainage of 'moisture from: the coil is periodically effected.

More specifically, it is an object of the present invention to va y the periods during which the coil is in operationandput of operation in accordance withthe humidityof the space in such a manner that drainage of moisture from the surface of the coil-is-assured during periods of high humidity, and during periods of low humidity, the moisture deposited on the surface of the coil will re-evaporate, thus increasing the sensible cooling effect of the coil. Another objectof the invention is the provision of a temperature responsive means for controlling conditioning apparatus, the temperature responsive means having a variable differential, and adjusting thedifierential in accordancewith the humidity of the space. v I

Another object of the invention is the provision of a temperature responsive means having means v for anticipating a change in temperature in a space, and varying the efl'ectiveness of the means for anticipating the efiect of a change in temaccordance with another condition in the space. Other objects and advantages will become ap* parent upon'a studyof the specification, claims, and appended drawing wherein is illustrated a preferred embodiment of my invention.

Referring more particularl t the drawing, an air conditioning chamber represented by the reference character It! is connected by means of the inlet opening II with thespace l2 to be conditioned. Air is drawn through the chamber by means of the fan l4 driven by a motor through the outlet 16. For ventilation purposes, fresh air'may also be drawn into' the chamber I!) through. the fresh airinlet l1 and the proportions of fresh and return air drawn into, the chamber I may be regulated by means of the dampers l8 and I9.

Located within the chamber I0 is a cooling coil over which the air flowing through the chamber passes. This cooling coil may comprise an evaporator of a refrigeration system, which system is shown to comprise a compressor 22 driven 'by a motor 23. Compressed refrigerant flows from the compressor through the discharge pipe 24 into a condenser 25 wherein the refrigerant'is condensed, the refrigerant then flowing into the receiver 26 and thence by Way of the pipe 21 and expansion valve 28 into the distributing header 29 of the evaporator 20, which is illustrated as being of the multiple pass type. The evaporated refrigerant from the evaporator 20 flows into the collector 30 and through the suction pipe 3! intothe low-pressure side of the compressor 22. The expansion valve 28 is illustrated as'being' of the thermostatic expansion valve type, the operating mechanism for the valve including a diaphragm or bellows 33, one side of which is connected by means-of the capillary tube 34 with a bulb 35 located in contact with the pipe 3| leading from the evaporator 20, in the manner well known in the art. If desired, the valve may be provided with an external equalizer connection as is common in the art. The expansion valve thus controls the flow of-refrigerantinto the evaporator 20 in a manner to prevent liquid refrigerant from flowin back into the compressor 22. The operation of such a refrigeration system is well known in the art and further description'thereof is believed to be unnecessary.

' means (not shown).

l5, the air being discharged into the space The compressor motor 23 is under-the control of a relay designated by the reference character 40 and which relay comprises a relay coil 4|, an armature 42, switch arms 43 and 44 connected to the armature 42, these switch arms cooperating with fixed contacts 45 and 46, respectively. n the ay c il is energized, the switch arms 43 and 44 move into engagement with their respective contacts, and upon deenergization of the relay coil the switch arms move out of enagement with their respective contacts under' the influence. of gravity .or any suitable biasing The circuit to the compressor motor also includes a' pressure responsive device 50'which comprises a bellows 5! connected by a tube 52 into'the pipe 24 connected-to the discharge side of the compressor. The bellows 5| controls the position of an arm 53 pivoted at 54 and carrying a mercury switch 55, the arm being biased downwardly by means of the .spring. 56. ;As long as the pressure of there'frigerant leaving the compressoris not excessively high the mercury switch will be in the-circuit closing position as illustrated. Should the pressure on the high pressureside of the compressor become excessively high however the expansion of the bellows 5| caused thereby will move the mercury switch 55 into the circuit breaking position. Line wires 58 and 59 supply power to the compressor ature at the thermostat 65 responsive device.

motor 23 when the relay 4! is energized and the mercury switch 55 is closed, the circuit being. as follows: from the line wire 59 through conductor 60, switch. arm 44, contact 46, conductor 9|, mercury switch 55, conductor '62, motor 23 and conductor 63 to the line wire 59, the line wires being connected to a suitable source of power, not illustrated. It will therefore be seen that when the relay 40 is energized and the pressure on the high pressure side of the compressor is not excessive, the compressor will be placed in operation to circulate refrigerant through the evaporator 29.

The energization of the relay 401s under the control of a temperature responsive device 96 which, for purposes of illustration, is shown to comprise a bimetallic element 99 carrying a flexible contact arm 61 for cooperation with a fixed .contact 98. The arm 91 carries a second contact arm 89 for cooperation with a. fixed contact 10.

As the temperature in the space l2 rises, the

bimetallic element 69 causes the arm 91 to move towards the contact 99 and the contact arms 91 and 99 are so arranged with respect to their respective contacts that arm 81 will first engage contact 98 and upon a further rise in temperature at the thermostatic element the arm 99 will engage the contact", the resiliency of the arm 91 permitting movement of arm 69 into engagement with contact 10.

Power is' supplied to the relay 4!! by means of 98 moves upwardly the step-down transformer 15 which includes a 4 high tension primary I9 connected across the line wires 68 and 59, the transformer also including a low tension secondary 11. hen the temperthat contactarm 99 is in engagement with contact I0, relay coil 4| will be energized as follows: from one side of the transformer secondary 11 through conductor 99, bimetallic element 66, contact arm 99, contact v1ll, conductors 9|, 82, 83, relay coil 4|, and conductor 94 to the'other side of the secondary l1. Energization of. the relay moves the arms 43 and 44 into engagement with the contacts 45 and 49, respectively causing operation of the compressor as heretofore described and also completing a holding or maintaining circuit for the relay coil 4| which is independent of engagement of arm 99 of the thermostat with contact 19, this maintaining circuit being as follows: from one side of the transformer secondary I1 through conductor 90, bimetallic element ",switch arm 91, contact 99, conductors 89, '9, switch arm 49, contact 45, conductors 90, 93, relay coil 4|, and conductor 94 to the-other side of the secondary 11. It will accordingly be seen that after the relay 40 has been, energized by adjustable resistance 94whereby the heating effect of heater 92 may be adjusted. A humidity which may be of any suitable construction and is shown to comprise a hygroscopic element 91 which expands and contracts in response to variations in humidity of the air in the space l2, has the movable end sufliciently high so thereof connected with the pivoted arm 99 which cooperates with the resistance 94. A spring I90 causes movement of the arm 99 in a direction to maintain the humidity responsive device 91 under a desired amount of tension. As the humidity in the space increases, the element 91 will expand, thus permitting downward movement of the left end of arm 99 which increases the effectiveness of the resistance 94. Conversely, upon a decrease in the space humidity the arm to decrease the amount of the resistance 94 in series with the heating element92.

As the temperature arm 61 of the thermostat engages contact 99 a circuit is completed through the heating element 92- as follows: from one side of the transformer secondary I1 through conductor 90, bimetallic element 99, contact arm 61, contact 98, conductors 89, I02, heating element 92, conductor 99,

resistance 94, arm 99, conductors I09, 92, 83, relay coil 4|, and conductor. to the other side of the secondary I'I. Sufiicient current does not flow through this circuit to energize the relay coil 4| but the heating element 92 will start to heat up, and the degree to which it will heat up will depend upon the amount of the resistance 94 that is in series therewith. Thus if the humidity in the space is low and the amount of the resistance 94 in series with the heating element 92 is low, the element 92 will-heat up to a greater 1 extent than when the humidity in' the space is high. The energization of the heater 92 causes the temperature of the bimetallic element to increase more rapidly than the space temperature increases, with the result that the contact 99 will engage the fixed contact 19 sooner and at a lower temperature of space 12 than it normally would were the heater contact arm 69 engages the contact 'lliand the relay 49 is energized to operate the compressor,

the above described maintaining circuit for the v relay which includes the arm 43 and the-fixed Since. the bimetallic element 69 has .engagement of arm 69 with contact 10, it will remain energized until the arm contact effectively shunts out the heating element 92 so that practically no current now-flows through this element and it will cool down. been heated to a higher temperature than the temperature to which the space 12 has risen by the time contact 69 engages fixed contact I0 tostart the compressor, the temperature of element 68 will drop rather. rapidly when the heater 92 is deenergized. At some time before the space temperature drops tothe temperature setting atwhich-contactl'l dlsengages fixed contact 69, the temperature of the bimetallic element will have become equal to the space temperature sotbat the temperature to which the space is cooled at the end of a period of operation of the compressor will be the same regardless of the heater 92. The effect of the heater, then, is to reduce the effective operating differential of the thermostat.

Assume that the thermostat is so adjusted that contacts 89 and 19 do not make until the bimetallic element 66 is five degrees warmer than "the temperature at which contacts 61 and 99 make and that the compressor has been shut down due to disengagement of contacts 61 and '99. On a rise in temperature causing contacts 91 and 99 to engage, the heater 92. will be energized.- The temperature of the space l2 will continue to rise but I element will rise-at a greater rate so that when contacts 99 and 10 engage to start the compressor and deenergize heater 92, the space temperain the space l2 rises and a 92 not present. As the the temperature of the bimetallic' ture will not have risen five degrees as has the thermostatic element but some lesser amount, for example two to four degrees, depending on the setting of the rheostat 94 as positioned by the humidity responsive element 91. 7 Accordingly the operating differential of the thermostat will be varied in accordance with the humidity of the air in the space and when the humidity in the space is low the operating differential of the thermostat will be small but asthe humidity in the space increases, the operating differential of the thermostat will be likewise increased.

The air passing through the air conditioning chamber i and over the evaporator 20 will have its temperature reduced and the evaporator 20 may also remove latent heat from the air as will be evidenced by condensation of moisture on the evaporator coils. If the compressor is operated for a sufiiciently long period of time so much water will be deposited on coils 20 that it will run off. -As shown by the'drawing, the chamber It] may be provided with a sump I20 located below the evaporator coils 20, a suitable drain I2! be-' ing connected to the sump for removing the water of condensation as it drains from the evaporator.

Under conditions of high humidity substantially all of the resistance 94 will be connected in series with heater 92 thereby lessening the supply of heat to the thermostatic element 66 during the period when the space temperatureis rising. Since little artificial heat is being supplied to the thermostatic element, contacts 69 and will not make until the space temperature hasrisen through substantially the full differential of the thermostat. Consequently when the compressor is started, considerable time will be required to bring the space temperature down to the point where contacts 61 and 68 will break to shut down thecompressor. During the first portion of the operating period of the compressor moisture will be condensed out of the air'onto the evaporator coils 20. Continued operation of the compressor will cause more water to be condensed than can remain on the evaporator coils and the water will flow from the coils to the sump 520 and the drain l2! thus permanently removing moisture from the air.

Under conditions of low humidity" the heater 92 will be heated to a greater extent due to lessening of the effective value of resistance 94 as adjusted by the humidity responsive element 91. When the compressor is shut down and the contacts 61 and 68 are in engagement the space temperature will be rising but considerable artificial heat will be supplied to the bimetal element 66 by the heater 92. The effect will be that long before the space temperature has risen sufficiently to cause contacts 69 and 10 to make, heater 92 will have raised the temperature of the bimetal element 66 to this point. Since the compressor has been energized at atemperature very little above the temperature at which the thermostat will be satisfied, it will not have to' operate very long to bring the space temperature down to this point. As pointed out hereinbefore, the first effect of operation of the compressor is to cause precipitation of moisture from. the air on the evaporator coils 20. If the operating cycle is sufliciently short the compressor will be shut down before sufficient moisture has been precipitated on the evaporator coils to cause drainage therefrom. Under conditions of low humidity the period of operation of the compressor is so shortened that little if any moisture is permapressor is shut down, air' flowing past the evaporator will reevaporate any moisture which has not passed to the drain I20; This is not undesirable when the humidity is low because this reevaporation of moisture causes additional sensible cooling;

It will be seen that I have provided a control system for a cooling and dehumidifying apparatus which controls the amount .of moisture re-.

.moved from the air by varying the length of the suitable controls therefor such as a suction pressure controller might be added. It should therefore be understood that my invention is to be I limited only bythe scope of the appended claims.

I claim as my invention: I 1. In an air conditioning system for a space, means for reducing the temperature of the air in the space, said means including an evaporator differential, and means responsiveto the moisture condition of the air in the space for increasing the operating differential of the temperature responsive means as the moisture condition increases and decreasing the operating difierential of thetemperature responsive means as the moisture condition decreases, without substantially changing the value of the temperature main tained by said temperature responsive means.

2. In an air conditioning system for a space, means for reducing the temperature of the air in the space, saidmeans including an evaporator of a refrigeration system, means for causing a circulation of air past said evaporator and through the space to be conditioned, means controlling the space, said means including an evaporator of a refrigeration system, means for causing a circulation of air past said 1 evaporator. and

through the space to be conditioned, means controlling the operation of the refrigeration system,

u said means including a space temperature responsive means having a variable operating differential, means for causingthe temperature adjacent said temperature responsive means to nenthr removed from the air. Once the com- .fall more rapidly than the space temperature after operation of the refrigeration system has been initiated, and means responsive to the humidity of the air in the space for varying the operation of said last named means.

4. In an air conditioning system for a space, means for reducing the temperature of the air in the space, said means including an evaporator of a refrigeration system, means for causing a circulation of air past said evaporator and through the space to be conditioned, means controlling the operation of the refrigeration system, said means including space temperature responsive means having two pairs of sequentially engageahle contact members, means responsive to engagement of both pairs of contact members due to a risein temperature adjacent said-temperature responsive means to initiate operation of said refrigeration system, means causing said refrigeration system to :remain in operation until both pairs of contact members have been disengaged, local heating means adjacent said thermostatic means, means causing energization of said heating means only when the first of the pairs of contact members to engage are inengagement and the refrigerating'apparatus is shut down, and means responsive to the humidity of.the space being conditioned in control of the heating effect of-saidheati'ng means. p 5. In a system of the class described, space 'cooling means, temperature responsive means in control of said space co'oling means, said temperature responsive means having a variable oper ating differential, and humidity responsivemeans for increasing the operatingdifferential of the temperature responsive means when the space humidity is relatively high and for decreasing the operatin differential of the temperaturerespon sive means when the space humidity is relatively low, without substantially changing the value of the temperature maintained by said temperature responsive means.

6. In a system of the class described, space cooling means, temperature responsive means incontrol of said space cooling means, said temperature responsive means having a variable operating differential, and means responsive to increases or decreases in the humidity of the air in the space for increasing or decreasing, respectively, the operating differential a proportionate amount, without substantially changing the value aaeaoes means for varying the operating differential thereof, and means responsive to the humidity of the space being conditioned in control of said last named means to increase the operating'differen- 1 tial of the temperature responsive means as the humidity increases and to decrease the operating medium through said cooling coil, means for causing a circulation of air. over said coil and through a space to be conditioned, said cooling coil eifecting a removal of both sensible and" latent heat from the air passing thereover, space temperature responsive means in control of the flow of cooling medium through said cooling coil, local temperature changing means adjacent said temperature responsive means, means under the control of. said temperature responsive means operativeto render said local temperature changing means more effective when said temperature responsive means is 'in' one position than when said temperature responsive means is in another position to vary,' the operating differential of said temperature responsive means, and humidity responsive means for varying the effect of said local temperature changing means to inc'reasesaid operating differentiaI as the humidity increases and'to decrease said operating differential as the humidity decreases.

9. A method of conditioning airfor a space .which comprises removing sensible and latent v heat by passing unconditioned air at substantially constant velocity over an evaporator of a refrigerating system which is continually supplied during eifective periods of operation with refrigerant passing serially through said entire evaporator and at such arate of flow as to maintain a substantially constant degree of superheat at the outlet of said evaporator, intermittently rendering said evaporator eifective and ineifective. over a period of time during which said space requires cooling and regulating the total time consumed by said effective periods in accordance with the of the temperature maintained by said temperature responsive means;

'7. In a system of the class described, a cooling coil, means for causing a circulation of a cooling medium through said cooling coil, means for causing a circulation of air over said coiland through a spaceto be conditioned, said'cooling. coil effecting a removal of .both sensible and sensible heat load on said space during said period of time for maintaining the dry bulb temperature in said space substantially constant, increasing the duration of said effective periods upon an increase inspace humidity and decreasing the duration of said effective periods upon a 'decreasein space humidity without affecting the average temperature of the 'air leaving said evaporator, or the total time consumed by said said temperature responsive means including effective periods, whereby the amount of sensible heat removed from the air by said evaporator over said period of time will be unaffected by the.

humidity in said space.

- ALWIN B. NEWTON. 

